Update to latest hashbrown, fix determinism of build

[gnunicorn]

This PR updates hashbrown to the latest release (0.8.0).

In the 0.6 series hashbrown's default feature set activated the compile-time-rng-feature in ahash, the internally used hasher – which lead to non-deterministic builds even on the same system. In the latest series this feature is not enabled by hashbrown by default anymore. Updating to that series fixes that problem.

As far as I can tell, this could be released as a non-breaking patch release.

[codecov-commenter]

Codecov Report

Merging #90 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #90   +/-   ##
=======================================
  Coverage   99.58%   99.58%           
=======================================
  Files           1        1           
  Lines         962      962           
=======================================
  Hits          958      958           
  Misses          4        4           

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[jeromefroe]

Hi @gnunicorn, thanks for the PR! I'm happy to land this change, out of an abundance of caution though, I think I'll release it as a new minor version (i.e. 0.6.0). I just worry someone may have an edge case which causes the version bump to break for them. What do you think?

[Ralith]

When the major version is 0, cargo treats the minor version as the major version, so that should be a very safe approach.

[jeromefroe]

Will go ahead and merge this and then release 0.6.0.